Hi James, This might be frustrating, but look on the bright side: at least you got to use a whole slew of your gadgets trying to solve this one!
I have two ideas for you:
Idea 1) Having read everything else you tried, it seems that huge popping sounds like it could be the ignition sparking way too late - as in when the exhaust port is coming open already so almost all of the combusion energy is routed right out the pipe rather than pushing the piston down. There are two causes I could think of: a) the timing is set after TDC, rather than before TDC. That'd be so weird because your timing marks would be way off and you'd catch it, besides that probably wouldn't be enough to cause the huge popping, it would just be way down on power. b) the CDI unit that controls the ignition mapping is screwed up. When you hooked up the timing light to check for missing spark, did you aim it at the rotor to see if timing advances as the engine speeds up? It would be a dead giveaway if the ignition timing retarded as the RPM's increased.
Idea 2) Sell the bike on Ebay listed as completely restored with hundreds of detail hours spent, and only ran at 1/4 throttle for break in.
Good luck,
Jon
I did check the ignition advance with the timing light in the inspection hole and it seems to advance and retard with the rpm fine , the timing is set in position with a dowel on the outer case so the timing of it should be bang on although i did try it without the dowel in and moved it back and forth with it running as you said this just made it lack power (even more) so the dowel is back in at the minute anyway cheers Jon for the input much appreciated James